Disc brake cylinder groove with a recess consisting of three sector surfaces

Abstract

A disc brake having a brake caliper provided with a hydraulic actuating device including a brake cylinder and a brake piston. The brake piston is sealed relative to the brake cylinder by way of a sealing ring arranged in a surrounding annular groove of the brake cylinder. The annular groove is provided with a recess arranged in the transitional area between a groove wall and the cylinder surface. The recess is confined by at least three surrounding conical surfaces whose angles towards the cylinder surface increase progressively, starting from the surface which borders on the cylinder surface up to the surface which borders on the groove wall.

We claim: 
     
       1. A disc brake with a brake caliper which straddles the outside edge of a brake disc and brake pads arranged on both sides of the brake disc and which is provided with a hydraulic actuating device, adapted to press the brake pads to the brake disc and having at least one brake cylinder and a brake piston axially, displaceable within the brake cylinder, an elastic sealing ring arranged in a surrounding annular groove inside the brake cylinder which rests frictionally for sealing purposes on an outside surface area of the brake piston, the annular groove having a groove wall nearest to the brake pads which is generally perpendicular to the brake piston axis and a surrounding recess adjacent to the brake cylinder, said recess receiving the sealing ring which is elastically pressed by the brake piston as the latter is axially displaced when the brake is applied, said recess having at least three adjacent surrounding conical surfaces the cross-sections of which are generally straight lines, with the angles of the straight lines towards the brake cylinder axis increasing progressively, starting from the surface which borders on the cylinder surface to the surface which borders on the groove wall. 
     
     
       2. A disc brake as claimed in claim 1, wherein the first surface which borders on the cylinder surface and brake cylinder axis encloses an angle between 30° and 40°, the second surface enclosing an angle between 40° and 50° and the third surface enclosing an angle between 65° and 80°. 
     
     
       3. A disc brake as claimed in claim 2, wherein the first angle is 30°, the second angle is 45° and the third angle is 74°. 
     
     
       4. A disc brake as claimed in claim 2, wherein a first edge formed at the intersection of the first surface and of the second surface is a first distance of 0.1 mm-0.4 mm from the brake cylinder radius and, a second edge formed at the intersection of the second surface and of the third surface is a second distance of 0.5 mm-0.9 mm from the brake cylinder radius and a third edge formed at the intersection of the third surface and of the groove wall is a third distance of 0.8 mm-1.8 mm from the brake cylinder radius. 
     
     
       5. A disc brake as claimed in claim 4, wherein the first distance is 0.3 mm, the second distance is 0.6 mm and the third distance is 1.4 mm. 
     
     
       6. A disc brake with a brake caliper which straddles the outside edge of a brake disc and brake pads arranged on both sides of the brake disc and a hydraulic actuating device adapted to press the brake pads to the brake disc and having at least one brake cylinder and a brake piston axially, displaceable within the brake cylinder, an elastic sealing ring which is arranged in a surrounding annular groove inside the brake cylinder and which rests frictionally for sealing purposes on an outside surface area of the brake piston, said annular groove having a groove wall nearest to the brake pads which is generally perpendicular to the brake piston axis and a surrounding recess adjacent to the brake cylinder, said recess receiving the sealing ring which is elastically pressed by the brake piston as the latter is axially displaced when the brake is applied, the recess having at least three adjacent surrounding sector surfaces the cross-sections of which consist of adjacent sector arcs with different sector radii which jointly form a convex arched line. 
     
     
       7. A disc brake as claimed in claim 6, wherein said first sector surface borders on the cylinder surface and has, in cross-section, a first sector radius of 1 mm-1.5 mm, a second sector surface having a second sector radius of 0.9 mm-1.2 mm and a third sector surface having a third sector radius of 1.5 mm-2 mm.